PHP - Assigning values within if statements

Question

I read the other day that assigning values within if statements isn't such a great idea. To be honest i actually use this quite a lot e.g.

if(isset($_POST) && $post = $_POST) {
  print_r($post)
}

Any idea why that isn't optimal?

Answer 1

Not least because it's a common newbie mistake to forget that assignment and equality operators are different, so it can easily lead to confusion or difficult-to-detect bugs.

Readability of your code is more important than any micro-optimisations

Answer 2

Because it is not about being optimal, it is about standards, conventions, the conditions need comparisons not assignments.

Don't Create The Confusion, Noobs might sit for hours debugging the issue !

Answer 3

Well, being alone, assignment in the logical operator is not that bad:

if ($id = $_GET['id']) {

or

while($row = mysql_fetch_assoc($res)) {

we use pretty often.
Though it's still in danger of readability fault or mixing = and == operators.

But mixing logical and assignment operators in one statement is bad. This is called obfuscation and perl write-only style, makes reading this code harder.

So, it's better to be written as

if(isset($_POST)) {
  $post = $_POST;
  print_r($post);
}

though this particular statement is pretty senseless.
$_POST is always set in any sensible environment and assigning it to another variable not necessary most of time